Issues in Achieving Precise Positioning Indoors Without Support from GNSS

Hemish K. Parikh, Abhijit Navalekar, William R. Michalson

Abstract:	It is well known that precise positioning indoors is a difficult problem due to presence of multipath. Less well known are the error components which effect positioning accuracy and how multipath contributes to total navigation system error. The focus of this paper is on an indoor positioning application for locating and tracking fire fighters inside a burning building. The fire fighter user community ideally requires indoor accuracy of less than one meter, with accuracies between three and six meters considered acceptable. This stringent accuracy requirement makes the design of indoor positioning systems challenging. Various RF and non-RF based prototypes that claim to be suitable for locating fire fighters indoors, can be found in the literature. Most of the existing literature summarizes the positioning results that were achieved using atleast one LOS component. Moreover, none of the existing literature provides a break down of the total navigation system errors observed with an objective of analyzing the contribution of each of error source independently. This paper will first provide a brief overview of an RF prototype system developed at the Worcester Polytechnic Institute. The field tests and observed indoor positioning results using this RF prototype will then be summarized and used to provide a baseline for establishing a system error budget. Following this, the main focus of the paper will be a discussion of important (but often forgotten/ignored) factors, other than the obvious problem with multipath, that impact these indoor positioning systems. The total observed error will be broken down and a detailed analysis of each of the error sources will be presented based on actual measured data in a variety of indoor environments. This will lead to better understanding on the effect of each error source on indoor positioning accuracy. Each of the error sources can then be independently optimized to minimize the observed errors. This paper will conclude by presenting an error budget which can be used as a practical lower bound while designing precise indoor positioning systems.
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	871 - 876
Cite this article:	Parikh, Hemish K., Navalekar, Abhijit, Michalson, William R., "Issues in Achieving Precise Positioning Indoors Without Support from GNSS," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 871-876.
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